It’s never a bad time to adopt healthy new habits for the mind and body, and for developers, it’s always a good time to consider new best practices at work. As 2023 rolls on, I’ve been thinking about some key performance metrics that help to ensure critical applications and websites perform optimally throughout the year—especially during unpredictable spikes.
To see why this is important, just look at the problems Ticketmaster had in November 2022 when Taylor Swift’s concert tickets went on sale. Fans of the pop idol (including me!) swamped the Ticketmaster site and brought the system to its knees, resulting in frustrated customers and a wave of bad publicity for the company.
These usage spikes and the problems they can produce are not uncommon. The holiday sales period, starting with Black Friday and Cyber Monday, is notorious for technical issues that can cost retailers millions due to lost sales and other problems. And it’s not just retail. A few years ago, the Internal Revenue Service (IRS) had to extend its tax deadline after a rush of last-minute filers knocked its systems offline.
Fortunately, developers can mitigate these problems with the right planning and practices in place. There are key performance metrics that developer teams should monitor, especially in times of peak traffic, to avoid application crashes, long wait times—and burnout for the teams who have to fix these problems when they arise.
Here are the five performance metrics developers should be tracking in 2023—especially on their busiest days of the year.
Web Vitals
The largest contentful paint, or LCP, measures the load speed of a webpage. Having a fast LCP is a clear sign that a customer’s experience is optimal as they toggle between pages. In tandem, the cumulative layout shift, or CLS, scores how a user is experiencing unexpected layout shifts. This plays out on busy shopping days: Typically, these pages have ad and sales notifications that affect a brand’s main page layout, potentially causing shoppers to experience unexpected shifts. This can reduce their ability to shop and becomes a hindrance if a developer cannot quickly access and address the issue.
Error Count Vs. Error Rate
Error counts typically increase alongside site traffic as more people flock to a website—that’s a natural occurrence. The error rate is more telling because it reveals if a greater proportion of users are experiencing issues with your application or website. Developers who see an increase in this metric should investigate and take action.
Mobile Monitoring
More and more consumers are using their mobile devices to shop and manage all aspects of their lives. For example, mobile accounted for 45% of sales during the holiday shopping period in 2022 from October to December. Mobile performance metrics are critical to understanding what is happening on your users’ devices during these busy times. Vitals like frozen and slow frames or cold and warm starts when an app opens provide visibility into how fast views are loading for your users. As became obvious with the Taylor Swift incident, a slow shopping experience can lead to an outcry and a lot of upset customers.
Outside of vitals related to mobile performance, it’s important to monitor mobile changes through application release health. Developers can see this in the rate of crash-free sessions and crash-free users as traffic to an application increases—which helps to identify abnormalities in the overall health of the app.
Slow Database and HTTP Ops
During sustained traffic spikes, database queries and HTTP requests that take too long to execute harm the user experience. Hitting a slow checkout process, or seeing the dreaded spinning beach ball after adding a product to the cart, confuses shoppers. They don’t know if they should refresh the page, and often they will abandon a purchase completely.
What’s more, if a developer is working on a backend framework, slow database and HTTP ops could also be a sign of an N+1 query problem. At that point, an application is making database queries in a loop and causing performance issues for the purchaser.
User Misery
This is a homegrown metric we use at Sentry; tracking user misery helps developers understand a customer’s experience with an application. It is a ratio of unique users who have experienced load times at 4x a configured threshold in a Sentry project and thus serves as a proxy for customer frustration. With this user misery score, our developers can see which transactions have the highest negative impact on users and prioritize fixing them.
Providing a smooth end-user experience is table stakes for businesses throughout the year, but especially during high-pressure, culturally-driven spending moments. In any of these scenarios, developers behind the scenes often work long and odd hours to address performance issues and ensure the most seamless experience. You can’t prepare for everything that can possibly go wrong, but you can be equipped with the right tools and metrics to quickly identify and remediate any problems that occur.
